DOS clients slow on Samba 4.1.7+ (bug 10422)

Dominic Raferd dominic at
Fri Oct 10 07:41:52 MDT 2014

On 10/10/2014 14:26, Volker Lendecke wrote:
> On Fri, Oct 10, 2014 at 02:08:30PM +0100, Dominic Raferd wrote:
>> Sorry I am not a Samba technical expert, but I believe there is a
>> new and quite severe bug for Samba 4.1.7+ introduced by bug fix
>> 10422. Although intended to cope with max xmit > 64kb it is having
>> unintended negative consequences for legacy client machines using
>> DOS.
>> This message appears hundreds of thousands of times in logs (even
>> with log level 0), and file accesses are slow slow slow:
>>    reply_read: requested read size (1024) is greater than maximum
>> allowed (972/1024). Returning short read of maximum allowed for
>> compatibility with Windows 2000.
>> The problem seems to be that samba has max_send is 972 and the new
>> bugfix code therefore blocks a *read* size of 1024. However the
>> connections for these clients always worked perfectly before with
>> the old test (which was against *max_recv* instead of max_send)
>> (e.g. with Samba 4.1.5).
>> The protocol my DOS clients are using is what Samba calls 'LANMAN2'
>> (Microsoft Networking).
>> I have tried different smb.conf settings (max xmit, socket options
>> SO_SNDBUG and SO_RCVBUF) and also varied settings on the DOS
>> clients, all to no avail. My conclusion is that Samba 4.1.7+ is
>> broken, or at least badly wounded, for these clients.
>> I would be very grateful if it could be fixed!
> Can you send a network trace of such a client? Please
> include the start of the connection. Please see
> Thanks,
> Volker

Hi Volker,

Yes I think I can do that with tcpdump, do I just zip it up and post it 


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